A variable valve mechanism includes: an outer arm; an inner arm provided inside the outer arm; a switching device that switches between a coupled state in which the inner arm and the outer arm are coupled together and a non-coupled state in which this coupling is released; and a lost motion spring that biases the inner arm toward a cam in the non-coupled state. Examples of a document describing such a variable valve mechanism include Patent Document 1 and Patent Document 2 described below.
In Patent Document 1, a lost motion spring is hooked, from the outside of an outer arm through a portion above the outer arm, onto an inner arm disposed inside.
In Patent Document 2, a slot (long hole) extending in a swinging direction of an inner arm is formed in an outer arm. A spring hooking portion formed on the inner arm in a protruding manner protrudes through the slot to a side of the outer arm. A lost motion spring is hooked onto the spring hooking portion on the side of the outer arm.